Injection pump arrangement for combustion engine



3,425,403 INJECTION PUMP ARRANGEMENT FOR COMBUSTION ENGINE Filed July 26, 1966 I M. G. MAY

Feb. 4, 1969 Sheet Feb. 4, 1969 I M. G. MAY

INJECTION PUMP ARRANGEMENT FOR COMBUSTION ENGINE Filed July 25, 1966 Sheet II I lnventor; P11241221 Nai Filed July 26, 1966 Feb. 4, 1969 INJECTION PUMP ARRANGEMENT FOR COMBUSTION ENGINE Sheet 3 of 4 M. G. MAY 3,425,403

Feb. 4, 1969 v i M. G. MAY 3,425,403

INJECTION BUMP ARRANGEMENT FOR COMBUSTION ENGINE Filed July 26, 1966 Sheet 4 of 4 &

lr7ventar:

United States Patent 0 M 66,130 U.S. Cl. 123-139 Int. Cl. F02m 49/00; F02b 3/00; F02d 3/00 20 Claims ABSTRACT OF THE DISCLOSURE The usual flow type carburetor for supplying fuel and air to a piston type internal combustion engine is replaced by a fuel system in which a diaphragm type fuel pump is operated by gas pressure pulsations occurring during piston movements, preferably transmitted through a fluid link connection from the engine to one side of the pump diaphragm. Fuel from the other side of the diaphragm is fed under pressure and in metered amounts directly through a conduit to a fuel injection nozzle discharging into the engine air intake adjacent a movable air throttle valve. Movement of this valve operates a fuel metering rod in the nozzle to vary the rate of fuel flow in relation to rate of airflow past the throttle valve in the idle range of throttle positions.

The present invention relates to a fuel injection arrangement for injecting measured amounts of fuel into the suction conduit of a combustion engine through which air is supplied, and more particularly to an injection pump provided with a membrane for pumping the fuel into the air supply conduit.

It is one object of the invention to provide an inexpensively manufactured reliably operating injection pump arrangement for a combustion engine which assures the supply of accurately measured amounts of the fuel to the combustion engine.

Another object of the invention is to provide an injection pump which is controlled depending on the amount of air supplied to the combustion engine, to pump such an amount of fuel into the combustion engine that the fuel-air mixture is substantially in a stoichiometric ratio.

Another object of the invention is to provide a fuel pump which is operable in different angular positions.

A related object of the invention is to provide a fuel injection pump which is particularly suitable for a combustion engine driving a saw for felling trees, which requires operation of the apparatus in different angular positions.

With these objects in view, the present invention provides an injection pump with a pump chamber through which fuel is pumped by a membrane oscillated by a pressure medium in a control chamber closed by the membrane. The pressure of the medium is controlled by at least one variable depending on the operation of the combustion engine in such a manner that the pressure varies in synchron'ism with the number of revolutions of the combustion engine, and that the pressure amplitude depends on the amount of fresh air sucked into the combustion engine during a suction stroke.

In accordance with the invention, the properties of the membrane which determine the output of the fuel pump, the flow resistance of the fuel in the conduits through which it flows, and the pressure amplitude of the pressure medium are selected and adjusted in relation to each other so that the weight of the fuel pumped in a time unit while the combustion engine is under a load, and the 3,425,403 Patented Feb. 4, 1969 weight of air sucked into the combustion engine in a time unit, are substantially in a stoichi'ometric ratio. The fuel pumped by the injection pump is injected through a nozzle directly into the air supply conduit of the combustion engine.

In-accordance with one embodiment of the invention, the fuel injection pump is combined with a combustion engine having an air supply conduit, and a chamber means filled with a fluid medium whose pressure varies cyclically in synchronismwith the operational cycle of the combustion engine and is a measure of the weight of air supplied to the combustion engine in a time unit during a suction stroke. The injection pump preferably comprises casing means having a first inlet for the medium and a second inlet and an outlet for a fuel; nozzle means communicating with the outlet and opening into the air supply conduit for producing a fuel-air mixture for the combustion engine; a membrane in the casing means forming in the same a control chamber communicating with the first inlet and being filled with the medium, and a pump chamber communicating with the second inlet and with the outlet and being filled with the fuel; and suction valve means and pressure valve means in the pump chamber controlling the second inlet and the outlet.

When the membrane is displaced by pressure variations of the medium in the control chamber, it pumps fuel through the pump chamber to the nozzle means and into the air supply conduit.

The membrane is arranged and constructed in accordance with the flow resistance of the fuel and the pressure changes of the medium so that the weight of the fuel pumped into the air supply conduit while the combustion engine operates under a load, is in a substantially stoichiometric ratio to the Weight of the air supplied through the air supply conduit to the combustion engine.

The injection arrangement of the invention substantially corresponds to a positive displacement pump, but special means for measuring the pumped amount of fuel can be omitted when the properties of the membrane which determine the output of the pump are selected in accordance with the fuel conduit system and the magnitude of the pressure amplitude of the actuating medium. For this purpose, a preferably adjustable throttle can be provided in the fuel conduit system, which at the same time effects a pressure increase of the fuel in the pump chamber, which is advantageous. The magnitude of th pressure amplitude of the pressure medium, which is a function of the weight per time unit of the amount of air sucked into the combustion engine, and consequently of the output of the combustion engine, can also be adjusted and regulated by suitable means. The properties of the membrane regarding the amount of pumped fuel are particularly determined by the area and stiffness of the membrane. While in special cases a diaphragm having no resiliency and consequently no rigidity against bending may be used as a membrane, it has been found that gener'ally stiff and rigid membranes, particularly metal membranes, preferably consisting of a copper beryllium alloy have particular advantages.

In order to further improve the exactness of the measured amounts of fuel supplied by the injection arrangement, in accordance with the present invention, an air chamber can be provided upstream of the suction valve, or downstream of the pressure valve, or at both places. Air chambers render the delivery characteristics of the injection pump more uniform, and regions within which very little fuel is pumped are eliminated. Furthermore, due to the provision of a pressure air chamber, the fuel is not intermittently, but continuously injected into the air flowing to the combustion engine, which is particularly advantageous.

Due to the low inertia of the membrane, an injection pump according to the present invention is particularly suitable for combustion engines operating at a very high number of revolutions. Furthermore, it has been found that the injection pump can also perform the function of a fuel pump, so that a separate fuel pump may be omitted.

The valves in the pump chamber may be of any suitable construction which prevents clogging by impurities, for example ball valves or vibrating valves may be used.

The injection arrangement according to the invention is particularly suited for a combustion engine which is placed in different angular operational positions during operation, for operating tools, such as pit saws, agricultural machinery, and similar apparatus.

The injection of the fuel into the air supply conduit system of the combustion engine is preferably carried out by a nozzle mounted in a wall of the air supply conduit. It is particularly advantageous that the nozzle is disposed at the height of the throttle flap, or throttle valve slide controling the supply of fresh air in the suction conduit of the combustion engine.

As mentioned above, the injection pump of the invention measures the amount of injected fuel. In some cases, however, it is desirable that under certain operational conditions of the combustion engine, an increased or reduced amount of fuel is injected, either for correcting the amount of fuel supplied by the injection pump, or for obtaining a special ratio between fuel weight and air weight in the fuel air mixture, which is for example desired when the combustion engine idles. This can be obtained by suitable control means influencing the amount of pumped fuel, and varying the throttle resistance of the nozzle, or the flow resistance of the conduits between the pressure valve and the nozzle, depending on a suitable variable representing the operational condition of the engine. In a preferred embodiment of the invention, the cross section of the nozzle opening is adjustable by means of a needle, which is fixedly secured to the throttle slide. Control means of this type are particularly suited for producing a rich fuel-air mixture in an operational condition of the combustion engine between idling and partial load.

It has been found particularly advantageous that the nozzle needle reduces the cross section of the needle while the combustion engine idles. The resulting higher pressure in the fuel pressure conduit system has a favorable influence on the insensitiveness of the apparatus to changes of its position. Furthermore, the delivery characteristics at lower speeds are additionally improved and rendered more uniform.

In a further development of the invention, a regulating of the fuel-air ratio can be obtained by using a membrane whose natural oscillating frequency is slightly greater than the maximum number of revolutions of the combustion engine. When the number of revolutions of the engine is too high, the membrane performs oscillations at an extremely great amplitude so that an excess of fuel is pumped, which causes a reduction of the output of the engine. In this manner, rotation of the engine at excessive speed, overheating, and damage to the engine can be prevented.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a schematic elevation illustrating a four stroke combustion engine with an injection arrangement according to the invention;

FIG. 2 is a plan view of an injection pump used in the arrangement of FIG. 1;

FIG. 3 is a sectional view taken on line IIIIII in FIG. 2;

FIG. 4 is a sectional view taken on line IVIV in FIG. 2;

FIG. 5 is an exploded perspective front view of an injection pump according to FIG. 2;

FIG. 6 is an exploded perspective rear view of an injection pump according to FIG. 2;

FIG. 7 is an elevation, partially in section, illustrating a throttle valve used in the arrangement of FIG. 1; and

FIG. 8 is a fragmentary sectional view taken on line VIIIVIII in FIG. 7.

Referring now to the drawings, in which corresponding parts are illustrated by like reference numerals, and the flow directions are indicated by arrows, the combustion engine shown in FIG. 1 has a cylinder 10 whose piston 11 is shown in solid lines in its lower dead center position. The upper dead center position is shown in broken lines 12. An air supply conduit 13 through which fresh air is sucked into the combustion chamber 22 of cylinder 10 during the downward movement of the piston, is provided with a throttle valve arrangement which will be described in detail hereinafter with reference to FIGS. 7 and 8. An injection nozzle 15 is arranged in the region of the throttle valve arrangement 14 for injecting into air conduit 13 a predetermined amount of fuel pumped by an injection pump 16. The fuel is sucked out of a fuel tank 17 by means of a flexible gravity operated suction head 18 which tends to assume a position located at the lowest point of fuel tank 17 irrespective of the position of the same so that fuel will be sucked out of tank 17 as long as there is any left in the lowest portion of the tank,

The injection pump is constructed of five parts, namely a front part 26, a membrane 20, a middle part 27, a diaphragm 40, and a rear part 28, as best seen in FIGS. 5 and 6. Parts 26, 27, 40 and 28 are secured to each other by bolts, not shown, passing through bores in the corners of the several parts, and the membrane 20 is clamped between the adjacent parts 26 and 27.

When membrane 20 abuts the rear face of front part 26, a control chamber 30 is formed which is bounded by membrane 20, as best seen in FIG. 3. Control chamber 30 communicates with a first inlet 21 in the form of a conduit 21 opening in control chamber 30, as best seen in FIGS. 3 and 6. Inlet conduit 21 is connected with combustion chamber 22 in cylinder 10, as best seen in FIG. 1, and in the illustrated embodiment, conduit 21 opens in cylinder 10 in a region which corresponds to half the stroke of piston 11. The fluid medium enters control chamber 30 through inlet conduit 21 so that membrane 20 oscillates in accordance with the pressure changes in combustion chamber 22. It has been found particularly advantageous to provide inlet conduit 21 spaced the same distance from the end of the piston in the two dead center positions 11 and 12.

Combustion engines which are constructed to precompress the sucked in fresh air in the crankcase, have conduit 21 advantageously connected to the crankcase, not shown. The pressure variations of the fluid medium in the crankcase or cylinder of the combustion engine are synchronous to the operational cycle of the engine and represent the amount of fresh air sucked into the engine during a suction stroke of the piston.

The pressure variations of the medium in control chamber 30, act on the membrane to oscillate the same so that fuel in a pump chamber 29 provided in the front face of middle part 27, see FIGS. 3 and 5, is subjected to pressure variations. Pump chamber 29 has an outlet 73 which is closed by a pressure valve in the form of a flap 38 formed in the diaphragm 40, see FIGS. 4 and 6. A suction valve means 33, which includes a flap 34 consisting of a synthetic plastic material and a leaf spring 35, covers an inlet 43a opening into an inlet chamber 43 in middle part 27 communicating with a fuel inlet conduit 30 which is connected with the fuel tank 17, as shown in FIG. 1. Inlet chamber 43 is closed by diaphragm 40 which separates inlet chamber 43 from an air chamber 44 formed in the front face of rear part 28, as best seen in FIGS. 4 and 5.

Valve flap 38 of pressure valve in outlet 73 is biased by a coil spring 39 located in an outlet chamber 37 which communicates through connecting ducts 47, 48 with another outlet chamber 45 in rear part 28 which communicates with an outlet conduit 49. The amount of fuel discharged from outlet conduit 49 can be adjusted by a throttling screw 50, as best seen in FIGS. 3 and 5. A pressure air chamber 46 is provided in the front face of middle part 27, and is separated by diaphragm 40 from the outlet chamber 45 in end member 28.

The diaphragm consists of an elastic synthetic plastic foil and is clamped between the marginal portions of end part 28 and middle part 27 to fluid tightly separate the chambers in parts 27 and 28. Diaphragm'portion 80 is located between inlet chamber 43 and air chamber 44 of the suction air chamber device 41, and diaphragm portions 81 is located between outlet chamber 45 and air chamber 46 of the pressure air chamber device 42. Since the diaphragm transmits pressure variations of the fuel in the inlet and outlet chambers to the air enclosed in air chambers 44 and 46, the flow of the fuel is rendered uniform and turbulence is suppressed.

As is evident from the drawing, the effective area 81 of the diaphragm cooperating with the outlet air chamber is greater than the area 80 cooperating with the inlet air chamber which has been found advantageous particularly for small pumps.

The throttling resistance of outlet conduit 49 can be adjusted by throttle screw 50 to obtain a desired output of the pump.

As shown in FIGS. 1, 7 and 8, outlet conduit 49 is secured to the air inlet conduit 13 of the combustion engine in the region in which the throttle valve is provided. A valve casing 60 is clamped between two flanged portions of air inlet conduit 13 and has a guide slot 61 in which a throttle slide 62 is guided for movement between the position shown in solid lines in FIGS. 7 and 8 for closing the air inlet conduit 13, and a position 63 shown in broken lines in which the cross section of air conduit 13 is open so that air can freely flow into the combustion chamber 22 of the combustion engine during a suction stroke of piston 11. Throttle slide 62, 63 is operated by a gas pedal or handle in the usual manner.

A nozzle is secured to outlet conduit 49 of the injection pump, and is screwed into a portion of casing 60. Nozzle 15 has a tubular part 15a projecting into the valve chamber of casing 60 and cooperating with a needle valve 45 secured to throttle slide 62. In the completely closed position of throttle valves 60, 62, needle valve 65 is located in the tubular nozzle portion 15a and closes the same by a cylindrical portion so that no fuel can be injected into the chamber 61 of the closed throttle valve 60, 62. In this position, the combustion engine is stopped.

During idling of the combustion chamber, throttling valve slide 62 is partly withdrawn, so that the tubular outlet portion 15a is not completely closed by needle valve 65, but the free cross section of tubular nozzle portion 15a is reduced by the conical end of the needle valve 65 so that only a small amount of fuel is injected into the air supply conduit 13 which is partly opened by the partly withdrawn throttle valve slide 62. In this position of throttle valve 60, 62, 65, a lean fuel-air mixture is obtained, as is desirable for idling of a combustion engine. When the air supply conduit 13 is completely opened by the fully withdrawn throttle valve slide 62, needle valve 65 is located outside and spaced from the tubular nozzle portion 15a, as shown in broken lines, and consequently the full amount of fuel discharged by the injection pump 16 enters the air supply conduit and is mixed with the air in the same to form a combustible mixture in the proper ratio of fuel and air. During transition from idling to full load, the nozzle outlet tube 15a is already opened by needle valve 65 before air supply conduit 13 is fully opened by throttle valve slide 62 so that a particularly rich mixture containing the full amount of fuel pumped by the injection pump, and a comparatively small amount of air, is obtained, which is favorable for accelerating the engine.

In the closed position of throttle valve slide 62, a sealing ring 64 in a cutout of throttle valve slide 62 abuts the annular edge of tubular nozzle portion 15a so that the same is fluid-tightly sealed.

The amount of fuel pumped by the injection pump can be influenced and balanced in several ways so that the desired amount of fuel is pumped without requiring an additional fuel measuring device. In addition to the regulation of the fuel output obtained by adjustment of throttle screw 50, the pressure amplitude of the pressure medium in control chamber 30 can be influenced by throttling the free cross section of the inlet conduit 21 through which a fluid medium contained in cylinder 10 is applied to the pump chamber 29. In the illustrated embodiment, a throttling screw 66 is mounted in a threaded bore of front part 26 for reducing the cross section of inlet conduit 21. The construction and physical properties of membrane 20 are of particular importance for obtaining the properly measured amount of fuel. When, in accordance with the preferred embodiment, a comparatively rigid membrane resisting bending is used, the resistance of the membrane to bending has a substantial influence on the amount of fuel which is pumped, and therefore must be carefully selected, which can be easily accomplished by experimentation.

A combustion engine with the injection arrangement according to the present invention as illustrated in FIG. 1 is particularly suitable for use wit-h a saw for felling trees. It is necessary to place the saw in different angular positions during operation. If the combustion engine is in the upright position shown in FIG. 1 during a first operational condition of the tool, it has to be placed in a position turned 90 out of the plane of the drawing in another operational condition of the tool. In the first operational condition, the plane 70 in which the membrane is located is inclined at an angle a to the vertical line 71. In this illustrated position of injecting pump 16, the port 72 of the outlet conduit 73 which connects pump chamber 29 with outlet chamber 36, is located at the upper end of outlet conduit 73 so that air bubbles in the fuel in pump chamber 29 gather in a funnel-shaped enlarged portion of port 72 and flow through pressure valve flap 38 into outlet chamber 36 so that the pump chamber 29 is freed of bubbles. The angle on is preferably between 30 and 45.

In the position of injection pump 16 illustrated in FIG. 1, port 72 is not exactly at the highest point of pump chamber 29, but displaced in relation to the longitudinal direction of pump chamber 29 by 45 in the circumferential direction of the pump chamber. In this position, port 72 is still located in the upper portion of pump chamber 29 when the combustion engine and injection pump 16 are turned to another operational position, so that the pump chamber can also be vented in the other angular position, not shown, in which the plane 70 of the membrane is substantially vertical.

The illustrated embodiment of the injection arrangement of the invention has been described in connection with a one-cylinder combustion engine. However, the

, injection arrangement may be used with multicylinder combustion engines, and a single injection pump is sufficient for such an arrangement.

In the illustrated embodiment of the invention, the fluid medium in control chamber 30 which operates the membrane, is the gas mixture contained in cylinder 12. However, as explained above, it is possible to connect inlet conduit 21 to the crankcase of a combustion engine which operates in such a manner as to precompress the fluid medium in the crankcase in accordance with the operational cycle of the combustion engine.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of injection pump arrangements differing from the types described above.

While the invention has been illustrated and described as embodied in an injection pump having a pumping membrane operated by pressure variations of a fluid medium in a combustion engine to which fuel is supplied by the injection pump, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any Way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without ommitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In combination with a piston type combustion engine having an air supply conduit with a throttle valve in said conduit and chamber means formed in part by the piston of the engine and being filled with a fluid medium whose pressure varies cyclically in synchronism with the operation of the piston and in a degree depending on the air drawn into the engine during its suctionstroke, a fuel injection pump comprising casing means; a membrane in said casing means and forming in the same a control chamber and a pump chamber; first inlet means in said casing means communicating with said control chamber and connected to said chamber means of said engine; fuel supply means; second inlet means in said casing means communicating with said pump chamber and connected to said fuel supply means; fuel outlet means in said casing means and communicating with said pump chamber; fuel injection nozzle means opening into said air supply conduit adjacent to one edge of said throttle valve; a conduit connecting said fuel outlet means directly with said fuel injection nozzle means; and suction valve means and pressure valve means in said pump chamber controlling said second inlet means and said outlet means, respectively, whereby said membrane displaced by pressure variations of said fluid medium passing through said first inlet means into said control chamber pumps fuel from said fuel supply means through said pump chamber to said nozzle means to be injected by the latter into said air supply conduit.

2. The combination according to claim 1 wherein said chamber means is the crankcase of the combustion engine; and including an inlet conduit connecting said first inlet with said crankcase.

3. The combination according to claim 1 wherein said chamber means is the cylinder of said combustion engine; and including inlet conduit means connecting said first inlet with said cylinder.

4. In combination with a piston type combustion engine having an air supply conduit with a throttle valve in said conduit and chamber means formed in part by the piston of the engine and being filled with a fluid medium whose pressure varies cyclically in synchronism with the operation of the piston and in a degree depending on the air drawn into the engine during its suction stroke, a fuel injection pump comprising casing means; a membrane in said casing means and forming in the same a control chamber and a pump chamber; a first inlet in said casing means communicating with said control chamber and connected to said chamber means of said engine; fuel supply means; a second inlet in said casing means communicating with said pump chamber and connected to said fuel supply means; a fuel outlet in said casing and communicating with said pump chamber; suction valve means and pressure valve means in said pump chamber controlling said second inlet and said outlet, respectively; said casing means being further provided with an inlet chamber between said suction valve means and said second inlet, with an outlet chamber between said pressure valve means and said outlet, with a first air chamber adjacent said inlet chamber, and with a second air chamber adjacent said outlet chamber, and including diaphragm means separating said inlet chamber from said first air chamber and said outlet chamber from said second air chamber; fuel injection nozzle means opening into said air supply conduit; and a conduit connecting said fuel outlet directly with said fuel injection nozzle means, whereby said membrane displaced by pressure variations of said fluid medium passing through said first inlet into said control chamber pumps fuel from said fuel supply means through said pump chamber to said nozzle means to be injected by the latter into said air supply conduit.

5. The combination according to claim 1 wherein said pressure valves includes a flap portion of said diaphragm, and resilient means biasing said flap portion to move to a closed position.

6. The combination according to claim 1 wherein said suction valve includes a flap, and resilient means urging said flap to a closed osition.

7. The combination according to claim 4 wherein said casing means is formed with an outlet chamber directly downstream of said pressure valve, and with an air chamber having a flexible wall bounding said outlet chamber.

8. The combination according to claim 4 wherein said casing means includes a front part formed with said control chamber, a middle part having a front face formed with said pump chamber, and a rear face formed with an inlet chamber and with an air chamber, said membrane being located between said front part and said middle part, a rear part formed in the front face thereof with another air chamber and with an outlet chamber communicating with said outlet; and including a diaphragm clamped between said middle part and said rear part and separating said first air chamber from said outlet chamber, and said inlet chamber from said second air chamber.

9. The combination according to claim 4 wherein said casing means is formed with an outlet conduit connected with said outlet and having a port opening into said pump chamber, said port being disposed in the upper portion of said pump chamber in different operational positions of said injection pump so that said pump chamber is vented and air bubbles in said fuel in said pump chamber escape through said outlet conduit.

10. The combination accordng to claim 9 wherein said port is funnel-shaped.

11. The combination according to claim 1 wherein said combustion engine is adapted to be operated in two operational positions angularly spaced from each other an angle of substantially and means for securing said injection pump to said combustion engine for movement with the same between said operational positions; and wherein said membrane is located in a vertical position in the first operational position, and inclined to a vertical plane an angle between 30 and 45 in the second operational position.

112. The combination according to claim 1 and including a throttle valve in said air supply conduit for varying the amount of said sucked into said combustion engine; and wherein said nozzle means opens in the region of said throttle valve in said air supply conduit.

'13. The combination according to claim 12 wherein said throttle valve includes a movable valve slide for opening and closing said air supply conduit, and a valve element for closing said nozzle when said valve slide closes said air supply conduit, for partially opening said nozzle means when said valve slide partly opens said air conduit, and for fully opening said nozzle means when said valve slide fully opens said air supply conduit.

14. The combination according to claim 13 wherein said valve element is a needle valve secured to said valve slide; and wherein said nozzle includes a nozzle outlet tube into which said needle valve moves for closing said nozzle means.

15. The combination according to claim 1, and including adjustable throttle means for adjusting the cross section of said outlet for reducing the amount of pumped fuel preferably to 30% to 70% of the maximum output obtainable when said throttle valve means is fully open.

16. The combination according to claim 1 and including adjustable throttle means for reducing the cross section of said first inlet leading to said control chamber.

17. The combination according to claim 1 wherein said membrane is arranged and constructed to have a natural oscillation frequency which is greater than the maximum number of revolutions of said combustion englne.

18. The combination according to claim 17 wherein said membrane has such a thickness and shape that it has a predetermined rigidity and resistance against bending selected in accordance with the output of said injection pump.

19. The combination according to claim 4, wherein said casing means comprises separate front, middle, and rear parts connected to each other with said membrane fluid-tightly clamped between said front and middle parts, and including a diaphragm clamped between said middle and rear parts, said front part having a cavity extending from a rear face of said front part into the latter and defining with said membrane said control chamber, said middle part being formed at the side thereof facing said membrane with said pump chamber and at its opposite side with a pressure air chamber and with an inlet chamber separated from said pressure air chamber and communicating with said second inlet and through an air inlet conduit with said pump chamber, said rear part being formed at the side thereof facing said diaphragm with an air chamber separated by said diaphragm from said inlet chamber, and with an outlet chamber separated by said diaphragm from said air chamber and communicating with said outlet, said pressure valve means including a flap portion of said diaphragm covering said outlet conduit.

20. The combination according to claim '1 and including first adjustable throttle valve means for adjusting the cross section of said inlet, second adjustable throttle valve means for adjusting the cross section of said outlet, said throttle valve located in said air supply conduit being operable for opening and closing the same, said throttle valve including a movable valve member closing said nozzle means in the closed position of said throttle valve, and partially opening said nozzle means in a partially open position of said throttle valve for varying the ratio of fuel-air mixture, whereby the flow resistance of the fuel from the fuel supply means to said nozzle means, and the pressure of the fluid medium acting on the membrane may be varied in dependence on the characteristics of the membrane so that the weight of the fuel supplied through said nozzle means into said air conduit per time unit is in substantially stoichiometric ratio to the weight of the air supplied per time unit through said air supply conduit to said combustion engine.

References Cited UNITED STATES PATENTS 1,105,298 7/ 1914 Peterson. 1,376,201 4/1921 Harris 123-119 2,796,838 6/1957 Phillips 123-119 XR 2,863,435 12/1958 Syson 123-119 3,013,733 12/1961 Williams et al. 123-1399 XR 3,186,395 6/1965 Fuka 123-1399 3,190,271 6/ 1965 Gudmundsen 123-1399 FOREIGN PATENTS 437,853 11/ 1935 Great Britain.

LAURENCE M. GOODRIDGE, Primary Examiner.

US. Cl. X.R. 123-33, 

